Control track



jan. 16, i945. N LEvlNsQN 2,367,294

CONTROL TRACK i Filed April 12, 1944 ENVENTOR Prasad im, 1c. 194s UNITED srA'rEs yPA'rizN'r ori-ics coN'raoL 'mack Nathan Levinson, North Hollywood, Calif., asslgnor to Radio Corporation oi America, p corporation of Delaware Application April 12, 1944, Serial No. 530,702 4 Claims. (Cl. P19-100.3)

This invention relates to sound reproduction and particularly to a control track record for controlling the amplitude of reproduced sound.

In the art of exhibiting motion picture sound nlm, the reproduction of the sound portion of the nlm has been controlled in various manners to enhance the dramatic presentation of the picture. It has beenl found desirable to increase the volume of reproduction of certain sound sequences such as sounds of earthquakes, nres, avalanches, or the music of larger orchestras, choruses, etc. Sometimes certain portions of the dialogue are expanded in volume to introduce certain dramatic effects. The reproduced amplitude range has heretofore been increased by self-controlled expansion systems wherein the variations of thenormal amplitude of the sound record control the amplification of the reproducing system. One of the preferred methods, however, of increasing the amplitude range and controlling the amplincation of the reproducing system, is by the use of a separate control track for the signal track or record. i

One example of such a control track system which has been found to be particularly desirable is shown in Burrill, U. S. Patent 2,270,260, of January 20, 1942. The control track described in this patent is one of variable width interposed between the sprocket holes of the sound or sound and picture nlm. The sprocket holes produce a carrier current modulated in accordance with the proportion of opaque to transparent area in the lands between the sprocket holes. The light variations produced by such a control track are translated into electrical currents which are rectined, nltered, and applied to the gain electrodes of a variable gain ampliner. The derived currents may be used for various purposes one of which is to control the distribution of sound among several loud speakers and for the relative amplitude of reproduction from different speakers as disclosed and claimed in Patent No. 2,335,- 575 of November 30, 1943.

In my copending application, Serial No. 445,308, nled June l, 1942, an improved method of preparing a control track for any particular sound necord which accompanies a motion picture is disclosed and claimed, the present invention being directed to a preferred form of control track particularly for the expansion of dialogue. In the past, control tracks have been produced by recordlng them during the reproduction of the sound records, the amplitude or frequency of the control track following the variations of a volume control potentiometer made by an operator as he controlled the amplitude of the reproduced sound. 'I'his recording operation was -generally done during rerecording and, before the results thereof could be checked, it was necessary that the control track be developed and printed. If the control track was not correct and required modincation, it was generally necessary to record a new control track. Aftervthe nnal control track was obtained, it was printed to the soundtrack negative after which it was of no further use and was discarded.

The invention of my copending application provides an improved method whereby the control track is immediately available for a test check as soon as a determination has been made of the amplitude variations desired. while the control track is obtained in such a manner that it may be broken down and reused afterit has served its purpose, thus eliminating nlm waste. Although the method of preparing the control record and the record itself is shown in connection with a sprocket hole control track, it is applicable to other forms of control records such as variable fre'quency control tracks or where the control track is on a nlm separate from the sound or .picture nlm.

In my Patent No. 2,029,173, of April 28, 1936, I have disclosed and claimed a Asound record which is produced by the intercutting of different types of sound tracks or records, such as variable area and variable density sound tracks, to produce a wide range sound record of'high quality. The present invention utilizes the general principle of this former invention in that it is directed to a control track which is made up of a plurality of sections of prerecorded or prepared control tracks inter-cut in accordance with cues prepared during a rehearsal. After the control track has been .printed on the sound negative, the control track nlm may be broken down into its sections, which are returned to their respective original nlm rolls and used again to make other control records.

The principal object of the invention, therefore, is to provide an improved control track for a particular signal sound track, which control track may be used again for other sound tracks.

Another object of the invention is to provide an improved control track for a particular signal track, which control trackis available for immediate use in controlling the reproduction of the signal track.

Another object of the invention vis to provide,

a control track from a plurality of preprepared 5s tracks representing various amplifier gains by inter-cutting said preprepared control tracks to produce a particular control track action for a particular signal track.

Although the novel features which are believed to be characteristic of this invention are pointed out with .particularity in the claims appended hereto, the manner of its organization and the mode of its operation will be better understood by referring to the following description, read in conjunction with the accompanying drawing. in which:

Figs. l, 2, and 3 are views representing partial sections of lms f prerecorded or preprepared control records from which a particular control record is made;

Fig. 4 is a view of a partial section of a illm having a particular control track or record thereon and assembled from sections of prerecorded illm records, such as shown in Fig. 1, Fig. 2, and Fis. 3;

Fig. 5 is a view of a portion of a composite signal track and control track negative film;

Fig. 6 is a view oi' a portion of a nal composite lm bearing pictures, signal track, and control track;

Fig. 'I is a graph showing the variation in amplitude obtained from the various width control tracks, and

Fig. 8 is a preferred control track section particularly suitable for the volume control of dialogue.

Referring now to Figs. 1, 2, and 3, these figures show three prerecorded control tracks of the sprocket hole type. 'I'hat is, Fig. 1 is a print 5 having sprocket holes 6 and a control track 1, the width of the clear portion being of any predetermined width such as 40 mils. The print I0 shown in Fig. 2 may have a clear portion ll of 20 mils, for instance, while the .print I4 in Fig. 3 may have a clear portion I5 of 4 mils. Each of these prints may be in rolls of 1,000 feet or less and stored in a iilm library. Although only three prints are shown, there may be many intermediate prepared prints in which the width of the clear portions 1, Il, and l5 may vary in width by approximately 4 mils, 4 mils representing about 1 db. variation in -volume of the reproduced sound.

The relation between control track width and amplier gain for a preferred reproducing systern is illustrated by the graph shown in Fig. '7, wherein it is observed that a control track width variation from zero to 40 mils will produce a change in gain of the amplifier of db. the variation being linear over substantially the entire range, except as the width of track approaches 40 mils. Thus, substantially 1 db. of gain change is obtained by a 4 mil variation in the width of the control track, the plurality of prints such as shown in Figs. 1-3 being previously prepared and identified by track width.

In the illustration of these prints in Figs. 1 to 3, the widest width control track is shown in 40 mils, but it is possible to use a track varying up to 90 mils, which corresponds to the usual length of the scanning slit. or even a 110 mil track, which is the length of the sprocket hole, with a scanning slit of the same length. 'I'hese wider sound tracks may be used in systems such as shown in the above-identidad copending application, wherein several variable gain ampliiiers are employed, the wider region from 40 mils up being used to control one variable gain amplier and the region from 40 to zero mils being used to control another variable gain ampliiier. However. as

far as the present invention is concerned, it is applicable to control tracks of any and all widths, the tracks being prepared in the same manner, regardless of their manner of use in the reproducing system.

In Fig. 4 is shown a composite control track il which has been made up of sections of control tracks of different widths. For instance, the lefthand end of the track has a clear portion 18 of 90 mils, in case the reproducing system is designed to use a control track of this width. The next section shows a control track 20 of 40 mils width which may be Fig. l, followed by a control track section 220i 20 mils as shown in Fig. 2, then a section 23 of 4 mils as shown in Fig. 3, and then a section 24 of 12 mils, the sections being shown broken from each other to illustrate that they may be of various lengths depending on the length of the sound sequences of the signal track. This control print is prepared as follows:

The signal track for which the control track is to be prepared is reproduced either alone or in conjunction with the projection of the picture which it will accompany. During the reproduction of the signal track, the operator, who is called a mixer. will vary the amplitude of various sequences as the sound is reproduced, the mixer making a record not only of the amount of variation in the gain, but the point on the signal nlm at which he made the gain change, this point usually being shown on a film counter within the mixers observation. Thus, as the signal sound track record is reproduced, the mixer vari the gain to increase or decrease the normal volume of the sound in a manner which he considers will enhance the telling of the story, making notes of the amount of these gain variations and their position on the signal track. These notes now become a cue sheet which is taken to the lm library where the various prints such as shown in Figs. l. 2, and 3 are kept. Now, from these prints various sections of the proper length are cut and spliced together to produce a control record such as shown in Fig. 4. The signal track is then again reproduced under control of the assembled control track sections, the mixer observing the amplitude variations and if necessary, making further changes therein of which he makes note. These new cues are again sent to the library and the control track modiiled accordingly, which is very quickly accomplished.

After the control track print is thus prepared, it is sent to the printer where it is used as a mask or a negative for printing the signal track negative such as shown in Fig. 5. 'I'hat is, a lm negative of the sound record to be used for printing release prints is prepared by recording on this lm a signal track which is made up of the various sounds required for the picture. 'I'hat is, the cue sheet and control track may -be prepared during the rerecording rehearsals where ,the sound is produced from a'plurality of lm records, such as a dialogue track and sound eiect tracks, or, after such rerecording has been done. In either case, however, track 28 of film 21 in Fig. 5 is the composite signal track negative use for printing release prints. 'I'he control track is printed to negative 21 and will appear as shown at 30l in Fig. 5. 'I'he longitudinal spacing of the control and sound tracks along the nlm may be in the neighborhood of Il frames as in an amount depending on the spacing of the respective pickup elements. 'I'his negative 21 is then developed and is used in producing the ilnal composite print 32 as shown in Fig. 6, which comprises the picture section 33, the signal track section 34 and the control track section 35.

As illustrated in Fig. 4, the widths of the track sections shown may vary from 90 mils'to 40 mils to 20 mils to 4 mils to 12 mils. This will correspond to gain changes of 22.5 db., 10 db., 5 db., 1 db., and 3 db., respectively. Now when volume increases and decreases are made in sound eiects such as earthquakes, fires, flood, storms, etc., gain changes of these amounts or greater may be made suddenly with the proper effects by directly joining adjacent sections of the desired Widths. However, for appreciable level increases and decreases in dialogue, it has been found desirable to produce a more gradual change between the various levels and this is accomplished by joining together a short series of one db. strips. Such a control track section is shown in Fig. 8 in which the Widths of the tracks on the adjoining sections 31--42 between sprocket holes, for the purpose of illustration, vary by 4 mils or one db., it being understood that these sections may be several sprocket holes in length. In this manner a smooth transition either up or down is obtainable between two levels of'considerable diierence without introducing distortion. A smooth reduction in volume may be obtained similarly by joining short sections 43-446 together, adjacent sections or strips varying by 4 mils.

til it becomes torn or worn out. In this manner,A

no extra ilm is required for the production of a control track after the library has been prepared. while any particular control track is available immediately after preparation of the cue track, thus saving time in checking each rehearsal and in obtaining the final control track.

It is to be understood that although the inven-y tion has been described in connection with prepared control track rolls varying in width of substantially 4 mils, the width of the tracks on the preprepared rolls may vary in any other manner, depending on the transmission characteristics of the reproducing equipment.

I claim as my invention:

l. A preconstructed control track for controll ling the reproduced Volume of a signal track, said ance with claim 1 in which said strips vary in width by substantially 4 mils.

3. A preconstructed control track for controlling tlie reproduced volume of a signal track beyond the normal range of said signal track comprising a series of prerecorded control track strips of lengths and widths corresponding to the lengths of time and predetermined volume levels of a signal to be reproduced, control track strips for varying the reproduced volume more than one db. being joined by a series of shortcontrol track strips Varying from one another by a volumevcontrol of substantially one db.

4. A preconstructed control track in accordance with claim 3 in which said strips have a variable area control track thereon, a variation of 4 mils in track width corresponding to substantially one db. in reproduced volume variation.

' NATHAN LEVINSON. 

